The significance of hot-dip galvanized steel coil

The significance of hot-dip galvanized steel coil

Cold-formed thin-walled steel has been generally used black material, after cold-rolled through a simple rust coating process go into service, and its service life is subject to certain restrictions (usually in about 5 years there will be a large area of rust). The company introduced to the market galvanized steel coil,based on hot-rolled strip, pickling, cold-rolled, heating and reduction, galvanized and other processes produced, and its products can reach the standard GB510018-2002 " technical specifications Cold-formed thin-walled steel structure," is mostly used in the construction industry , but also in the automotive, railway locomotive manufacturing, warehouse board manufacturing, highway guardrail and other industries.

Galvanized hydrogen reduction is invented in 1937, hydrogen reduction method of hot-dip galvanizing laid the basis for a modern continuous hot-dip galvanizing.Production by technology Hydrogen reduction method, the appearance of quality, bonding of zinc layer are better than the solvent method of galvanizing. Galvanized Reduction method in steel strip after pickling into the heating reduction furnace, with hydrogen after restoring produce oxide film  , and in pickling and heating reduction process to produce a layer of sponge-like steel surface layer, into the zinc pot can produce a layer of zinc-iron alloy layer with good bonding strength and uniformity, which greatly increases the adhesion of the zinc layer, which also determines the high energy consumption cost of the zinc plating method.

Galvanized solvent method Ammonium chloride was invented in 1837. The product by technology solvent method Ammonium chloride , due to the Galvanized solvent method Ammonium chloride without heating reduction process, the appearance of the quality and galvanized surface adhesion is worse than Galvanized Hydrogen reduction method . This also determines the cost of energy consumption of its zinc plating method lower than galvanized  hydrogen reduction .

三、  galvanized amount of Galvanized steel coil  sheet is generally 180-220g / ㎡, in the wet southern region can increase the amount of galvanized to 275g / ㎡ to improve the life of steel components. The life of galvanized products is generally 20-25 years.

四、  characteristics Zinc layer of galvanized steel
Electro-galvanized layer can not form zinc spangle, hot-dip galvanized layer has  zinc spangle, the formation process is as follows:When the galvanized strip comes out from the zinc pot, a large amount of zinc liquid is blown back to the zinc pot by blowing of air knife. At this moment, there is still pure zinc layer on the surface of the steel strip, which is attached to the surface of the steel sheet by  the liquid state to form a large amount of crystals on the surface of steel sheet , with the steel sheet cooling up, so that the crystalline nuclei slowly grow into zinc spangle.The faster the cooling rate, the smaller the zinc spangle, the slower the cooling rate, the greater the zinc spangle.

Zero spangle galvanized sheet:

In fact, Zinc spangle has only ornamental value, no practical value, on the contrary in the anti-corrosion is not good, in developed countries have implemented small zinc spangle and  zero spangle galvanized steel sheet.